Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only show readOnlyHint=false, so the description carries the burden of explaining behavior. It reveals that the tool does not upload itself; it returns a presigned URL that the caller must PUT to, and that the resulting URL feeds create_post. It omits details like URL expiration or storage-host requirements, but covers the core non-obvious workflow.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the primary condition and purpose, with no filler. Every sentence adds actionable information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given two simple parameters and no output schema, the description covers the invocation workflow, the fallback path, and the downstream create_post usage. Missing only minor operational details such as presigned URL expiration or size limits.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description should compensate. It never mentions filename or contentType, leaving their formats and constraints undocumented. The parameter names are self-explanatory, but no meaning is added beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Description states a specific purpose: get a presigned URL for uploading media via HTTP PUT, then use it with create_post. It distinguishes itself from the sibling upload_media by calling itself the 'Preferred media path' for PUT-accessible runtimes.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly says when to use this tool ('when you can HTTP PUT') and when not to ('If your runtime cannot reach the storage host ... call upload_media instead'). It also gives the exact sequence: PUT file bytes to the returned URL, then pass the public URL to create_post.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.